Office machines for processing text data to produce hard copies utilize display screens for presenting to an operator visual text as it would appear on hard copy. Typically, such machines incorporate a conventional typewriter keyboard with additional control keys for operator interface with the system controls. The operator keystrokes are displayed on a screen quite similar to a home television receiver screen. This screen either displays a full page of text, a partial page, or in some machines only a single line of text. The display not only provides a visual presentation to the operator of the text being prepared but also provides prompting instructions for the operator of how to interface with the machine.
Responding to the keyboard strokes of an operator are system controls including programmed computers which prepare the text display. Most present day text processing systems include electronics hardware programmed to evaluate the operator keystrokes and to control the display. This electronics hardware includes memory for storing character data and instruction data for future use in editing and the preparation of hard copy. Ease of operation of the machine for the operator is in large part determined by the electronics and the associated computers and programs therefor.
One area of importance in determining the ease with which an operator interfaces with a machine is the movement of a cursor, that is, an identification mark on the screen indicating a character position. A cursor is used by an operator in text editing functions including the insertion of additional characters into text, identifying characters or blocks of characters to be moved, deleted or copied, and the reformatting of the text display. Heretofore, many text processing systems restricted the cursor motion to displayed text. That is, to move a cursor from one part of a screen from another required the cursor to be moved line by line through the displayed text. When such machines utilize formatted text stored memory, this restriction on cursor motion was found acceptable. However, the use of unformatted memory for storing character or instruction data resulted in the inefficient use of storage space and compromised the requirement for large storage capability in memory.